The present invention relates to an optical inspection apparatus for detecting particles and surface defects on electronic or magnetic substrates. More particularly, the present invention relates to an apparatus for imaging the entire substrate within an integrated processing environment.
The presence of contaminant particles on the surface of electronic substrates such as semiconductor wafers can lead to the formation of defects during the microelectronics fabrication process. In order to maintain high manufacturing yield and thus low manufacturing costs, it is necessary that contaminated wafers be identified and cleaned during the manufacturing process.
In general, wafer inspection systems have been configured as highly sensitive, stand-alone inspection systems which typically have dedicated material handling systems for handling the substrates to be inspected. These systems are designed to provide sensitivity to extremely small defects and particles. This is generally accomplished by minimizing the background scattering from the surface either by using a small laser spot size (in laser scanning systems) or a high magnification objective lens for camera based inspection systems. In addition, many of these inspection systems use special techniques to minimize background scatter when inspecting patterned substrates, such semiconductor wafers formed by photolithography etching and deposition process steps. These systems are thus complex in design and expensive. The high cost of these inspection systems necessarily means that the number of such systems present in production lines is low. As a result, inspections for particles and defects are relatively few and far between. Since a very large number of process steps are involved in the processing of electronic substrates, the low frequency of wafer inspections between process steps may lead to contaminated substrates remaining undetected for a long period of time. This leads to lower yield and increased rework costs.
The present invention addresses these and other problems, and offers other advantages over the prior art.